The main objectives of this research project are the study of the physiological actions of cyclic nucleotide stimulated protein kinases, as well as the control of their activity. This will include: (1) The identification of the protein kinases present in muscle, and the study of their differential characteristics, (2) The study of the mechanisms of control of protein kinase activity, both by covalent structural changes of the enzyme (phosphorylation-diphosphorylation), and by intracellular components. The aim is to correlate the effect of hormones with their controls, (3) The action of protein kinases on physiological substrate proteins present in the tissue. Primarily, the study of the control of muscle contraction by mechanisms of phosphorylation-diphosphorylation of the contractile proteins.